1. Field
The present disclosure relates to a method and a system for correcting at least one uniformity error selected from the group consisting of a process direction uniformity error and a cross-process direction uniformity error in an image printing system that prints on an image bearing surface movable in a process direction.
2. Description of Related Art
A cross-process direction uniformity in an image printing system may be affected by one or more subsystems in the image printing system. For example, these subsystems may include a charge subsystem, an imaging subsystem, a development subsystem, a transfer subsystem, and a fusing subsystem. Instead of making all these subsystems in the image printing system very uniform over the width of the process it is generally more effective to correct for temporally stable non-uniformities by adjusting the power of the laser used to form a latent image on the image transfer photoreceptor belt or drum. The prints can be made darker where needed by locally boosting the laser power. In other words, for the image printing systems that do not create a uniform-within-page image, the laser power across the image may be adjusted to generate a more uniform image. For direct imaging systems (e.g., an inkjet or a liquid wax printing system), the dot size may be locally adjusted by changing adjustable parameters for each individual nozzle. For example, an adjustable parameter for the individual nozzle may include heating current. Alternatively, the adjustment may also be made by changing the halftone level locally in the digital front end.
In high end image printing systems, these adjustments are done by measuring the cross-process direction density profile of a halftone print. The measured profile is then automatically downloaded into an imaging controller. For the lower end entry production image printing systems, these adjustments are done manually by visually evaluating a print and adjusting the laser intensity every 2 to 3 inches across the process. In other words, there is no measurement system in the lower end entry production image printing systems that is available to measure the non-uniformity. It is generally very difficult to assess low frequency color changes with this current manual procedure where a diagnostic print with full width halftone color strips is used.